What happens at the hotel that makes Daisy and Gatsby suddenly leave?

At the Plaza Hotel Tom finally confronts Gatsby, mocking his use of the phrase "old sport." Tom accuses Gatsby of never having been at Oxford; Gatsby replies that he did, in fact, study there for five months after the end of the war. Tom regards Daisy's affair with the lower-class Gatsby as one of the harbingers of the decline of civilization. Soon, Tom hisses, there will even be intermarriage between the races. Gatsby tells Tom that Daisy doesn't love him, and has never loved him; he informs him that he's "not going to take care of Daisy anymore." Tom calls Gatsby a "common swindler" and reveals that he has made his fortune in bootlegging. Daisy, in her shallowness and snobbery, sides with Tom, and refuses Gatsby when he pleads with her to say that she has never loved her husband. As the confrontation draws to a close, Nick realizes that today is his thirtieth birthday.